A liquid crystal display (LCD) generally consists of a layer of liquid crystal fluid (a substance which exists at a state between liquid and crystal), between two systems of electrodes. Typically, one or both of the electrodes are transparent and each of the systems is resident upon a transparent substrate. The two substrates are arranged in parallel fashion so as to form a sandwich. When electrodes are arranged so that selected portions of the electrodes may be energized while other portions remain neutral. An integrated circuit or driver is used to selectively energize the electrodes.
When the driver energizes the electrodes, the liquid crystal fluid between the electrodes exhibits hydrodynamic turbulence and disperses the light. The contrast between the dispersed light transmitted and/or reflected light, creates the figures or characters in the display.
Liquid crystal fluids are roughly classified as into three types; smectic, cholesteric, and nematic. The nematic type of liquid crystal fluid has proved to be the most useful for LCDs. The interior surface of each of the substrates in the LCD contains an alignment layer that has a series of minute grooves that are preferentially oriented in a given direction. The liquid crystal molecules immediately adjacent to each of the plates align themselves with the direction of orientation of an alignment layer, that is, they align themselves with the minute grooves. Those molecules that are between the plates orient themselves into a helix, the ends of which correspond with the alignment direction on each plate. When the plates are at right angles to each other, the helix makes one quarter of a turn which results in linearly polarized light traversing the cell being rotated through an angle of 90.degree.. In the usual construction, the cell is sandwiched between an upper and a lower polarizing plate or polarizing filter. These polarizing plates are placed on the exterior side of each of the two substrates. Assuming the axes of the polarizing plates to be a right angles to each other, incident light will then be transmitted through the cell due to the optical activity of the liquid crystal material between the plates.
When the axes of the polarizing plates are parallel to each other, no light can traverse the cell. However, when an electric field is applied to the selected electrodes by the driver, the liquid crystal composite will lose its optical activity because the axis of the liquid crystal molecule aligns parallel to applied electric field. Because the polarizing filters are placed at right angles to each other, as the optical activity is lost from the selected portions of the fluid, those portions become opaque, while the remainder of the cell remains transparent. Of course, if the polarizing filters are parallel, the converse takes place.
Because the appearance of the character or element in the display is simply a change between transparent and opaque, the characters tend to have a flat, two-dimensional appearance. Efforts have been made to enhance the two-dimensional black and white appearance of LCDs by adding color filters and by other methods that introduce color into the display. However, the use of color filters results in a monochromatic display that still has a two-dimensional quality and color displays tend to be complex and expensive. It would be a significant addition to the art if a liquid crystal display could be fabricated that would provide an enhanced appearance without the added complexity and expense imposed by color LCDs.